Project help: Arduino Powered Bluetooth Key Finder

  • I want to make a small key finder with ATtiny 45 AVR(microcontroller) ,hc-05 Bluetooth module and buzzer.
    #How can I make a microcontroller stability circuit.

    #Please tell me about the circuit connections.

    #should i want to connect external oscillator circuit
    block diag

  • @Geethesh welcome to makergram. It's is great to know that you are gonna build a ble keyfinder. Let me point out few things to build a ble keyfinder. First of all battery is a main part of a keyfinder. So you should use low power consumption components and modules to build your hardware. HC05 will use pretty much power. So hc05 is not recommended for low power applications. instead you can use an ble module which will works on low energy. A recommended chip is nrf51822 SoC. Wich comes with built in ble. The most using SoC for ble applications in market. Basically you can find it in bluetooth keyboards and mouse. Attiny45 is a good microcontroller for low power applications but I would recommend you to use a ble SoC chip. I didn't get what for the reset button. Can you explain a little bit?

  • @Suhailjr thank you for the help ,is HM-10 is ble .
    i have edited(deleated) the question about the reset .
    plese tell me will hm -10 works for me

  • @Geethesh Hello. First of all greetings from makergram community. I would like to brief you with the architecture aka block diagram that you've mentioned.

    1. The microcontroller which you are trying to use is good for the application. Your choice of component is very appreciable.

    2. Regarding the connection diagram, to answer your question should i want to connect external oscillator circuit my answer is NOO. Because if you look into the datasheet of the Attiny85(same as ATtiny45) you can notice that it has an On-Chip 8MHz oscillator 👇. So, you can breathe now as you don't have to put an external oscillator circuit. Don't worry about the timing issues, they are industry calibrated.


    1. Coming to the architecture part, I suggest you not to use HC-05 because it is a Classic Bluetooth. You cannot use them for BLE applications. So, HM-10 can be used for BLE applications. I guess if you have made an little research about this project on youtube you will come across this video Bluetooth Key Finder Video link Please watch this video where he makes a similar project of finding keys in the room using his BLE remote.

    Please reach us in case of queries. All the best..!!

  • @kowshik1729 thank you for replay

  • Hi @Geethesh, If you are building simple POC (Proof of concept ) or Quick prototype then the HC-05 is enough with the ATtiny.

    • For the ATtiny45 minimum circuit you only need one Pull up resistor for Reset, and one Filter capacitor between VCC and ground and you also need to populate ICSP pins for programming

    • You also need only two external componts HC-05 and Buzzer .

    • In the this project we did't require any external oscillator , the internal 8mhz should be fine .

  • @salmanfaris thank u for the details and circuit

  • @Geethesh , keep in mind ATtiny series doesn't have Hardware Serial, so you should use the SoftwareSerial for that you also need two more for UART communication (Rx, Tx) between Arduino and Bluetooth.

  • @Geethesh In case if you live near kalamassery(where Fablab is situated) I strongly suggest to go to Fablab where you can find all the necessary tools and IC's required.

Log in to reply

Recent Posts

  • @Suhailjr But I think since it's not a plug and plug play system and it will laying on the PCB for the long term, it might be fine. for me, it's similar to the Intel Edison and the PICO-IMX7 System-on-Module



    read more
  • @salmanfaris at last they update their design. T
    What you think on the updated connector. I felt like its more fragile and high chance for corottion issue due to humidity for long term use.

    read more
  • Built on the same 64-bit quad-core BCM2711 application processor as Raspberry Pi 4, Compute Module 4 delivers a step-change in performance over its predecessors: faster CPU cores, better multimedia, more interfacing capabilities, and, for the first time, a choice of RAM densities and a wireless connectivity option.


    You can find detailed specs here,

    1.5GHz quad-core 64-bit ARM Cortex-A72 CPU VideoCore VI graphics, supporting OpenGL ES 3.x 4Kp60 hardware decode of H.265 (HEVC) video 1080p60 hardware decode, and 1080p30 hardware encode of H.264 (AVC) video Dual HDMI interfaces, at resolutions up to 4K Single-lane PCI Express 2.0 interface Dual MIPI DSI display, and dual MIPI CSI-2 camera interfaces 1GB, 2GB, 4GB or 8GB LPDDR4-3200 SDRAM Optional 8GB, 16GB or 32GB eMMC Flash storage Optional 2.4GHz and 5GHz IEEE 802.11b/g/n/ac wireless LAN and Bluetooth 5.0 Gigabit Ethernet PHY with IEEE 1588 support 28 GPIO pins, with up to 6 × UART, 6 × I2C and 5 × SPI


    Compute Module 4 IO Board

    The IO board provides:

    Two full-size HDMI ports Gigabit Ethernet jack Two USB 2.0 ports MicroSD card socket (only for use with Lite, no-eMMC Compute Module 4 variants) PCI Express Gen 2 x1 socket HAT footprint with 40-pin GPIO connector and PoE header 12V input via barrel jack (supports up to 26V if PCIe unused) Camera and display FPC connectors Real-time clock with battery backup

    More details:,

    read more
  • 28e1870e-33fe-4791-bc74-05c9d58098da-image.png

    Seeed is currently counting down for the 10 year anniversary of the debut of Grove 🎉. In the past 10 years, we have seen many wonderful projects created by Grove from our user and community. We want to invite you to join us to celebrate the 10 year anniversary of Grove 🤩.

    In the Grove 10 Years Celebration, we’d like to collect the stories of “Grove with You”, which we want to invite our users to share their stories they have with Grove products.

    => What project you’ve made out of Grove?
    => What is your favourite Grove?
    => which one was the first Grove you’ve purchased?

    Seeed encourages you to post and share photos, videos, stories of Grove in the Seeeed Forum, or any other platforms below that you’d like to use.

    The following ways to find us, and tag #grove10 to share the project with us!

    Twitter (@seeedstudio) Instagram (@seeedstudio) or simply email your project to

    Feel free to be creative in documenting your projects–we will be selecting top 10 most “Grovy” winning entries from the submissions, and the winners will receive a $100 Grove Surprise Pack 😋 as a special gift.

    Looking forward to seeing your projects! 🥳

    read more
  • @kowshik1729 I think that might not get since the platform is not opensource! but they provided everything you need to develop a system with that.

    read more